Affinity partitioning, a new affinity purification method for receptor-rich membranes, will be further developed and applied to the purification of neurotransmitter receptor-rich subsynaptic membrane domains. Subsynaptic membranes from mammalian brain are known to contain high densities of saccharides. Purification will be based upon the interaction of plant lectins with saccharide-rich membrane fragments. Membranes purified by lectin affinity reagents will be further fractionated into classes that bind specific muscarinic cholinergic antagonists. By isolating neurotransmitter receptors and associated components in their membrane environment problems associated with solubilization and concommitant disruption of biological properties will be obviated. Membrane fractions obtained in these procedures will be characterized in terms of their protein and glycoprotein constituents. Evaluation of the hypothesis that neurotransmitter receptors mediate their responses by regulating enzymatic activities will be carried out by analysis of the purified neurotransmitter receptor-enriched membrane fractions.